CAN/CSA-Z243.56-88

Scope  

The principal use of the XID frame is to exchange data link information between two or more HDLC stations. For the purpose of this International Standard, data link information shall include any and all essential operational characteristics such as identification authentication and/or selection of optional functions and facilities concerning each station. This International Standard defines a single-exchange negotiation procedure for establishing operational characteristics when either one or more stations are capable of providing multiple selections.
 
This International Standard provides a means for interchanging the nece ssary information to establish, at a minimum, a data link connection between two correspondents wishing to communicate. It describes the general purpose XID frame information field content and format.
 
This International Standard does not limit or restrict the use of the XID frame information field from defining other standard formats for use in specific applications.
 
The following are examples of potential uses of the XID command/response frame interchange:

• Identification of the calling and called stations when using circuit switched networks (including switched network backup applications).
• Identification of stations operating on non-switched networks requiring identification at start-up.
• The XID command frame with an individual, group or all-station address may be used to solicit XID response frame(s) from other station(s) on the data link, prior to or following data link establishment.
• Convey higher layer information that may be required prior to data link establishment.
• Transmission of an XID response frame at any respond opportunity to request an XID exchange to modify some of the operational parameters (for example, window size) following data link establishment.